paintings, that quality U.S. products were preferable, and that only
high-quality chipboards should be used for reinforcement (Wolters
1952:20). Thinner plywood auxiliary backings for weak wooden supports
were also sometimes cradled to maintain an even configuration (SIK 1990).
Fiberboards were rarely used as auxiliary supports in panel paint-
ing conservation. Sundeala boards were used in 1958 as auxiliary supports
for thinned Gothic paintings.
Partial transfer to particleboard has been possible since about- An example is the portrait of Johann Caspar von Laubenberg by
Bernhard Strigel, acquired by the Kunsthalle Karlsruhe in 1955 (inv. 2375;
Lauts 1966:286). The thinned wooden panel is glued to particleboard, and
the back of this auxiliary support is covered with an oak veneer. In addi-
tion, a cradle is mounted (Koch 1981).
In the Wolters Report, particleboard is not recommended for use
as an auxiliary support because of its uneven surface (Wolters 1952:21).
According to Wiesmann-Emmerling, a treatment of the epitaph painting
of about 1420 for Count Dietrich von Wernigerode is documented in the
Hessisches Landesmuseum Darmstadt. The central painting was thinned
and reinforced with particleboard in the 1960s (Wiesmann-Emmerling 1994).
Other modern types of auxiliary supports in use since the 1960s
are frequently identical to those used for the conservation of transferred
wall paintings. These include aluminum honeycombed panels covered by a
fiberglass tissue and laminated with epoxy resin.
Materials for gluing auxiliary supports to original supports include
wax-resin mixtures or hide glue; wax-resin was preferred because of its
reversibility.
Installations and tools used to mount the thinned original panels on
the auxiliary supports with the use ofpressure are part ofthe joiner’s tech-
nical equipment. The use of veneer presses or similar constructions also
used for canvas painting relining seems to have been understood as a great
“improvement.” Since about 1968, the vacuum table has also been used.
Rejoining broken and cracked panels
Traditionally, rejoining broken and cracked wooden panel paintings was
considered the task of the joiner, perhaps working under the supervision
ofa painter-restorer (Hertel 1853:33). Welsch recommended flattening the
damaged portions of the painting before gluing (Welsch 1834:65). The
bonding medium was probably bone glue, hide glue, or casein glue. The
addition of natural resin such as colophony made these glues somewhat
water-resistant.
Numerous newtypes of glues became available in the early twen-
tieth century. Synthetic adhesives for cold application were attractive for
gluing wood. Kauritleim,a w atery dispersion of urea resins, was used with
a hardener (Gerngross and Goebel 1933:477).
Around 1950 environmental climatic conditions for the paintings
became the determining factor in the choice of glue. Normally most
German public conservation studios use neutral bone and hide glue, some-
times with added chalk or zinc oxide. In the process of gluing with hide
glue, the butt-joint surfaces of the panel were warmed slightly with
infrared spotlights. Casein glue is still frequently in use. The new synthetic
glue types were mentioned in the Wolters Report (1952:14–15). But
Brachert shows that animal glues are still in use (Brachert 1955b:19).224 Schiessl